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United States Patent |
5,244,033
|
Ueno
|
September 14, 1993
|
Diecasting apparatus
Abstract
A diecasting apparatus is mainly composed of: a mold unit having a movable
mold and a stationary mold both of which have mold cavities in the meeting
surfaces thereof and, also having an inlet formed at a lower portion of
the mold unit and a vertical passage extending from the inlet upward to
the mold cavity, and further having a sleeve connected to the inlet and
thus communicating with the mold cavities through the inlet and the
passage; and a supplying unit for supplying molten metal into the sleeve.
A supplying passage is provided in the stationary mold, and has one of its
openings at the inner surface of the inlet of the vertical passage, and
communicates with the outside of the stationary mold. A duct connects the
supplying passage and the supplying unit. A molten-metal heater is
provided on the duct. A valve mechanism for opening and closing the
supplying passage is composed of a valve seat and a valve. The valve seat
is provided in the supplying passage, close to the inlet or the vertical
passage, and is tapered so as to become wider toward the movable mold. The
valve is supported by the movable mold and is moved to and away from the
the valve seat by a driving unit.
Inventors:
|
Ueno; Toyoaki (Yamaguchi, JP)
|
Assignee:
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Ube Industries, Inc. (Ube, JP)
|
Appl. No.:
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853080 |
Filed:
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March 17, 1992 |
Foreign Application Priority Data
Current U.S. Class: |
164/312; 164/337 |
Intern'l Class: |
B22D 017/30 |
Field of Search: |
164/312,337
|
References Cited
U.S. Patent Documents
3248759 | May., 1966 | Burkett | 164/312.
|
3254377 | Jun., 1966 | Morton | 164/312.
|
4753283 | Jun., 1988 | Nakano | 164/312.
|
4795126 | Jan., 1989 | Crandell.
| |
4989663 | Feb., 1991 | Kitamura | 164/312.
|
4991641 | Feb., 1991 | Kidd et al.
| |
Foreign Patent Documents |
2947602 | May., 1981 | DE.
| |
3218326 | Dec., 1982 | DE.
| |
3222828 | Dec., 1983 | DE.
| |
57-39069 | Mar., 1982 | JP | 164/133.
|
62-207559 | Sep., 1987 | JP | 164/312.
|
62-286659 | Dec., 1987 | JP | 164/312.
|
63-84753 | Apr., 1988 | JP | 164/312.
|
Primary Examiner: Batten, Jr.; J. Reed
Attorney, Agent or Firm: Kanesaka and Takeuchi
Claims
What is claimed is:
1. A diecasting apparatus comprising:
a mold unit having a movable mold and a stationary mold both of which have
mold cavities in meeting surfaces thereof and, also having an inlet formed
at a lower portion of said mold unit and a vertical passage extending from
said inlet upward to said mold cavities, and further having a sleeve
connected to said inlet and thus communicating with said mold cavities
through said inlet and said passage;
a supplying unit for supplying molten metal into said sleeve;
a supplying passage provided in said stationary mold and having one of its
openings at an inner surface of said vertical passage and communicating
with an outside of said stationary mold;
a duct connecting said supplying passage and said supplying unit;
molten metal heating means provided on said duct; and
valve means for opening and closing said supplying passage, including a
valve seat and a valve, said valve seat being provided in said supplying
passage, close to said inlet and said vertical passage, and being tapered
so as to become wider toward said movable mold, said valve being supported
by said movable mold and being moved to and away from said valve seat by
driving means.
2. A diecasting apparatus according to claim 1, wherein said supplying
passage is provided with a check valve for preventing the molten metal
from flowing back to said supplying unit.
3. A diecasting apparatus according to claim 1, wherein said supplying unit
is provided with a check valve for preventing the molten metal from
flowing back from said mold unit.
4. A diecasting apparatus according to claim 2, further comprising a well
portion which stores the molten metal and which is provided at a halfway
portion of said supplying passage between said check valve and said valve
seat.
5. A diecasting apparatus according to claim 2, further comprising heating
means for heating the molten metal in said well portion.
6. A diecasting apparatus comprising:
a mold unit having a movable mold and a stationary mold both of which have
mold cavities in meeting surfaces thereof and, also having an inlet formed
at a lower portion of said mold unit and a vertical passage extending from
said inlet upward to said mold cavities, and further having a sleeve
connected to said inlet and thus communicating with said mold cavities
through said inlet and said passage;
a supplying unit for supplying molten metal into said sleeve;
a supplying passage provided so as to extend substantially horizontally in
said stationary mold and having one of its openings at an inner surface of
said vertical passage;
a duct having one of its openings at a bottom-side inner surface of a rear
portion of said supplying passage and communicating with said supplying
unit;
molten metal heating means provided on said duct; and
valve means for opening and closing said supplying passage, including a
valve seat and a valve, said valve seat being provided in said supplying
passage, close to said inlet and said vertical passage, and being tapered
so as to become wider toward said movable mold, said valve being supported
by said movable mold and being moved to and away from said valve seat by
driving means.
7. A diecasting apparatus according to claim 2, wherein said supplying unit
is provided with a check valve for preventing the molten metal from
flowing back from said mold unit.
8. A diecasting apparatus according to claim 6, wherein said supplying
passage inside the stationary mold is tapered so as to become gradually
wider toward said movable mold.
9. A diecasting apparatus according to claim 8, further comprising a rod
provided at a side of said supplying passage in the stationary mold, said
rod being slidable to be located in the supplying passage and having a gas
passage therein to provide a gas into said supplying passage.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a diecasting apparatus and, more
particularly, to a diecasting apparatus whose mechanism for supplying
molten metal is improved so as to be suitable for diecasting of magnesium
alloys.
2. Description of the Related Art
In a conventional diecasting apparatus comprising a supplying unit for
supplying molten metal into a sleeve, and a mold unit having an inlet
provided at a lower part thereof to which the sleeve is connected, a
molten metal passage (a runner portion) extending vertically and a mold
cavity communicating with the sleeve through the inlet and the molten
metal passage, a diecasting operation is performed by: supplying molten
metal into the sleeve; connecting the sleeve to the inlet at the bottom
portion of the mold unit; and raising a plunger to send (inject) the
molten metal stored in the sleeve into the mold cavity.
A ladle is used to pour molten metal into the sleeve after the sleeve is
detached from the mold unit.
For an easier method of pouring molten metal with the ladle, the sleeve is
tilted (e.g. as shown in FIG. 3 of Japanese Patent Publication No.
57-21414), or while being maintained vertically, the sleeve is moved away
from the bottom of the mold unit (e.g. as shown in FIG. 4 of the
above-mentioned patent specification).
FIG. 2 of the same patent specification shows a pouring method in which
while the sleeve is connected to the lower mold, the lower mold is
descended, and molten metal is poured from the ladle down into the
descended lower mold through the molten metal passage.
In the above-described ladle-pouring method in which the sleeve is detached
from the mold unit, a long interval is required between the pouring of
molten metal into the sleeve and the injection of the molten metal into
the mold cavity, and contamination is likely to occur. Further, in the
pouring method in which the sleeve is tilted, the capacity of the sleeve
cannot be fully utilized, so the sleeve must be made larger (longer) to
compensate for the dead volume.
In the pouring method in which molten metal is poured down through the
lower mold into the sleeve while the sleeve and the lower mold are kept
connected, the injection of the molten metal poured in the sleeve can not
be performed until the lower and upper molds are clamped. In other words,
it takes a long time before the injection. Also, while being poured
through the lower mold into the sleeve, the molten metal may spill on the
top surface of the lower mold, i.e. the mating surface thereof.
In any of the methods described above, the molten metal is exposed to the
atmosphere while poured into the sleeve, or even until the sleeve is
connected to the inlet in such a method. The molten metal may well oxidize
when exposed to the atmosphere. Thus, the above-described methods are
unsuitable for diecasting of metals which easily oxidize (e.g., magnesium,
aluminium and alloys thereof). Even in the case of diecasting of metals
which do not so easily oxidize, an oxide may be produced or trapped
therein to cause defects in the cast product.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide a diecasting apparatus
in which molten metal can be smoothly supplied into a sleeve without fear
of spillage.
It is another object of the present invention to provide a diecasting
apparatus which can cast easy-to-oxidize metals such as magnesium without
oxidization.
Still another object of the present invention is to provide a diecasting
apparatus which facilitates shortening the cycle of the diecasting
operation.
The further objects, features and advantages of the present invention will
become apparent in the below description.
A diecasting apparatus according to the first aspect of the present
invention comprises, a mold unit having a movable mold and a stationary
mold both of which have mold cavities in the meeting surfaces thereof and,
also having an inlet formed at a lower portion of the mold unit and a
vertical passage extending from the inlet upward to the mold cavity, and
further having a sleeve connected to the inlet and thus communicating with
the mold cavities through the inlet and the passage; and a supplying unit
for supplying molten metal into the sleeve. Such a diecasting apparatus
further comprises: a supplying passage provided in the stationary mold and
having one of its openings at the inner surface of the inlet of the
vertical passage and communicating with the outside of the stationary
mold; a duct connecting the supplying passage and the supplying unit;
molten metal heating means provided on the duct; and valve means for
opening and closing the supplying passage, including a valve seat and a
valve, the valve seat being provided in the supplying passage, close to
the inlet or the vertical passage, and being tapered so as to become wider
toward the movable mold, the valve being supported by the movable mold and
being moved to and away from the valve seat by a driving means.
A diecasting apparatus according to the second aspect of the present
invention, comprises: a mold unit having a movable mold and a stationary
mold both of which have mold cavities in the meeting surfaces thereof and,
also having an inlet formed at a lower portion of the mold unit and a
vertical passage extending from the inlet upward to the mold cavity, and
further having a sleeve connected to the inlet and thus communicating with
the mold cavities through the inlet and the passage; and a supplying unit
for supplying molten metal into the sleeve. Such a diecasting apparatus
further comprises: a supplying passage provided so as to extend
substantially horizontally in the stationary mold and having one of its
openings at the inner surface of the inlet of the vertical passage; a duct
having one of its opening at bottom-side inner surface of a rear portion
of the supplying passage and communicating with the supplying unit; molten
metal heating means provided on the duct; and valve means for opening and
closing the supplying passage, including a valve seat and a valve, the
valve seat being provided in the supplying passage, close to the inlet or
the vertical passage, and being tapered so as to become wider toward the
movable mold, the valve being supported by the movable mold and being
moved to and away from the valve seat by a driving means.
In a diecasting apparatus according to the present invention, the valve
means is opened and molten metal is supplied form the supplying unit
through the inlet or the vertical passage in the mold unit into the
pouring sleeve while the pouring sleeve is connected to the inlet of the
clamped molds. When a predetermined amount of molten metal is supplied
into the pouring sleeve, the valve means is closed and the injection
plunger is raised to inject the molten metal into the mold cavity.
Thus, in a diecasting apparatus according to the present invention, the
injection of molten metal can be performed immediately after molten metal
is supplied into the pouring sleeve. During the supplying of molten metal,
spillage of the molten metal never occurs. Also, the sleeve can always be
positioned vertically so that molten metal can be poured up to the upper
edge of the sleeve. Thus, the length of the pouring sleeve can be made
minimal.
In a diecasting apparatus according to the present invention, molten metal
is never exposed to the atmosphere over the course thereof from the
supplying unit into the mold cavity. Therefore, even easy-to-oxidize
metals can be cast without any practical problems, and defects caused by
oxides are eliminated. Also, a diecasting apparatus according to the
present invention is very useful for diecasting molten magnesium alloys
which easily explode when exposed to the atmosphere.
Since the duct is provided with a heater, the molten metal left in the duct
stays melted and can be immediately used for the next supply. Thus, the
time required for the supplying operation can be substantially reduced.
In a diecasting apparatus according to the present invention, the supplying
passage is opened by moving the valve supported in the movable mold away
from the valve seat provided in the stationary mold and is closed by
moving the valve to the valve seat. The stationary mold is not provided
with a supporting member for slidably supporting the valve, and thus, the
sliding surface of the supporting member does not face the internal
surface of the passage. As a result, the sealing of the passage is secured
.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is vertical sectional view of a main portion of a diecasting
apparatus according to the first embodiment of the present invention.
FIG. 2 is an enlarged view of the main portion of the apparatus shown in
FIG. 1.
FIG. 3 is a vertical sectional view of a diecasting apparatus according to
the second embodiment of the present invention.
FIG. 4 illustrates a main portion of the apparatus shown in FIG. 3 during a
pouring operation.
FIG. 5 is a sectional view taken along line 5--5 in FIG. 4.
FIG. 6 illustrates the main portion shown in FIG. 4 during an injection
operation.
FIG. 7 illustrates the main portion shown in FIG. 4 when it is opened.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
The first embodiment of the present invention will be described with
reference to FIGS. 1 and 2.
A mold unit 10 comprises a stationary mold 14 fixed on a stationary board
12 and a movable mold 16 which is moved toward and away from the
stationary mold 14 (to the left and right in the figures), e.g., by means
of a toggle mechanism (not shown). An inlet 18 is formed at a bottom
portion of the mold unit 10 composed of the stationary and movable molds
14, 16. The inlet 18 is connected through a runner portion 20 to a mold
cavity 22. Through such a passage, a molten metal is introduced into the
mold cavity 22.
The inlet 18 is adapted to engage with the upper end portion of a pouring
sleeve 24. The pouring sleeve 24 is provided on an upper end portion of an
injection unit 26. An injection plunger 28 is fitted in the pouring sleeve
24. The injection plunger 28 is connected by a rod 29 to an injection
cylinder (not shown) which moves the injection plunger 28 up and down.
The inlet 18 is connected to the outside of the mold unit 10 through a
passage 30 which is formed in the stationary mold 14 so as to have one of
its openings at the inner periphery of the runner portion 20. Thus, molten
metal is supplied from an external source through the passage 30 to the
inlet 18. A valve means 32 is provided in the passage 30, near the inlet
18. The valve means 32 includes a valve seat 34 and a valve 38. The valve
seat 34 is tapered so as to become wider toward the movable mold 16. The
valve 38 is formed so as to be seated on the valve seat 34 and is movably
supported in the movable mold 16. The valve 38 is connected, by a screwing
means, to a rod 40 of a cylinder (a device for driving the valve means)
42. Instead of the cylinder 42, a solenoid may be used.
A well 36 is provided at a midway portion of the passage 30. The well is
composed of an inner liner 36a and a heat insulating member 36f wrapping
the inner liner 36a. The inner liner 36a comes into direct contact with
the molten metal and is formed of ceramic or heat resisting metal (e.g.,
SKD61). Induction heating coils (induction heater) 36b, 36c are provided
so as to surround the heat-insulating member 36f. Thus, the molten metal
in the well 36 can be heated by supplying current to the induction heating
coils 36b, 36c. The coil 36b is placed near the valve seat 34 and is
electrically separated from the coil 36c. By means of the coil 36b, the
temperature of molten metal close to the valve seat 34 can be controlled
independently from the rest of the molten metal in the well 36.
The well 36 is provided with a check valve 36d at the upstream end thereof.
The check valve 36d prevents a back flow of the molten metal.
The passage 30 is connected through a duct 44 to a supplying unit 46. The
supplying unit 46 comprises a tank 48 for storing molten metal and a pump
means 50 for pumping out the molten metal from the storing tank 48. The
pump means 50 is composed of a cylinder barrel 54, a piston 52 inserted in
the cylinder barrel 54, and cylinder 56 for moving the piston 52 up and
down. The storing tank 48 is connected through a suction inlet 60 and a
passage 58 to the inside of the cylinder barrel 54.
A rod valve 62 is provided at the suction inlet 60. A valve cylinder 64
moves the rod valve 62 up and down to open and close the suction inlet 60.
A check valve 68 is provided at a halfway portion of a passage 66. The
molten metal in the barrel 54 is conveyed through the passage 66 and the
check valve 68 to the duct 44. A heater 70 is provided around the duct 44.
In a diecasting apparatus constructed as described above, if the piston 52
is raised while the suction inlet 60 is open (the rod valve 62 is raised),
the molten metal M flows from the storing tank 48 into the barrel 54.
Next, the suction inlet is closed by the rod valve 62, and the valve 38 is
moved back to open the valve means 32. If the piston 52 is lowered in such
a condition, the molten metal M flows out of the barrel 54 through the
passage 66, the check valve 68, the duct 44, the passage 30 and the runner
portion 20 into the inlet 18. Preferably, the plunger 28 should be raised
as high as possible beforehand and be lowered gradually as the molten
metal M flows in.
When a sufficient amount of molten metal M is stored in the pouring sleeve
24, the valve means 32 is closed by moving the valve 38 to meet the valve
seat 34, and the injection plunger 28 is raised to inject the molten metal
M into the mold cavity 22. Despite pressure caused by the injection of the
molten metal, the check valves 36d and 68 according to this embodiment
prevent the molten metal from flowing back to the storing tank 48.
The above injection is followed by solidification of the molten metal,
opening of the molds, taking-out of the product and mold clamping. Then,
the molten metal is supplied to the pouring sleeve 24, as described above,
for the next diecasting. The molten metal remaining in the well 36 and the
duct 44 is maintained at a required temperature by the induction heating
coils 36b, 36c and the heater 70. The molten metal near the valve means 32
in the well 36 is in semi-solidified state, so that the molten metal
melted fully in the other part of the well 32 away from the valve means 32
does not flow out thereof toward the sleeve 24 even when the molds 12, 14
are opened. The semi-solidified metal is heated by the coil 36b and is
melted before and during the molten metal is supplied, so that the molten
metal is immediately supplied to the inlet 18.
Immediately after the molten metal M is supplied to the pouring sleeve 24,
the injection operation can be started simply by closing the valve means
32. Thus, the diecasting operation can be quickened, and an unnecessary
decrease of the temperature of the molten metal stored in the pouring
sleeve 24 can be avoided, so that partial solidification is also avoided.
As a result, the quality of the cast products is upgraded.
As can be understood from the illustration in FIG. 1, the molten metal
stored in the tank 48 is conveyed to the pouring sleeve 24 without being
exposed to the atmosphere. Therefore, even molten metal easy to oxidize,
such as aluminium or magnesium, can be cast without any oxidization,
according to this embodiment. A wide variety of metals can be cast, and
the defects caused by oxide are eliminated. As a result, high-quality cast
products are obtained.
Also as can be understood from the illustration in FIG. 1, the only place
where the molten metal can possibly leak is the portion connecting the
stationary mold 14 with the duct 44. Such a possible leakage is prevented
by employing a packing to seal the connecting portion. The packing
employed in this embodiment is durable enough to provide a
substantially-long-term sealing.
According to this embodiment, the cylinder 42 for moving the valve 38 to
join with the valve seat 34 has a long stroke so that the valve 38 can be
moved farther than the valve seat position when the mold is disassembled.
This long-stroke cylinder 42 facilitates the cleaning (e.g. fettling),
maintaining or replacing of the valve 38.
The valve 38, according to this embodiment, is provided with a cooling
means, e.g. of water-cooling type, in order to protect the valve 38 from
the heat of the molten metal. Also, such a cooling means can be used to
enhance the sealing of the valve means 32. When the valve means 32 is
substantially closed, the cooling means cools the molten metal between the
valve 38 and the valve seat 34 to increase the viscosity or the molten
metal or partially solidify it. Thus, leakage through the valve means 32
is substantially prevented. To open valve means 32, the molten or
solidified metal adjacent to the valve seat 34 is selectively heated by
the induction heating coil 36b.
As shown in FIGS. 1, 2, the inner liner 36a according to this embodiment
has the same inside diameter over its entire length. The valve seat 34 is
tapered so as to become wider downstream. Thus, there is nothing to block
or obstruct the smooth flow of the molten metal through the well 36 (or
the passage 30).
Since the movable mold 16 is moved horizontally away from the stationary
mold 14 (the horizontal mold type), according to this embodiment, when the
cast product is to be taken out, the solidified metal located from the
valve means 32 toward the inlet 18 can be taken out together with the
product.
As shown in FIG. 1, the pouring sleeve 24 according to this embodiment is
connected to the inlet 18 so that it is always positioned vertically and
never tilts during a diecasting operation. Thus, a substantial amount of
molten metal can be stored in the pouring sleeve 24. The pouring sleeve 24
does not need to be so long as that in a known art.
Although the passage 30 has one of its openings at the runner portion 20 in
the above embodiment, it may be directly connected to the inlet 18.
Although the pouring sleeve 24 is connected to the inlet 18 to assume a
vertical position in the above embodiment, the pouring sleeve 24 may be
connected to the inlet 18 which has its opening at the side surface of the
mold, to take a horizontal or diagonal position.
The second embodiment of the present invention will be described with
reference to FIGS. 3 through 7.
A mold unit 101 comprises a stationary mold 103 fixed on a stationary board
102 and a movable mold 105 which is moved toward and away from the
stationary mold 103 (to the left and right in the figures), e.g., by means
of a toggle mechanism (not shown). An inlet 106 is formed at the bottom
portion of the mold composed of the stationary and movable molds 103, 105.
The inlet 106 is connected through a runner portion 107 to a mold cavity
108. Through the inlet 106 and the runner portion 107, molten metal is
introduced into the mold cavity 108.
The inlet 106 is adapted to engage with the upper end portion of a pouring
sleeve 109. The pouring sleeve 109 is provided on the upper end portion of
an injection unit 110. An injection plunger 111 is movably fitted in the
pouring sleeve 109. The injection plunger 111 is connected by a rod 112 to
an injection cylinder (not shown) which moves the injection plunger 111 up
and down. The pouring sleeve 109 can be separated from the molds 103, 105
by lowering the sleeve 109 from the position thereof shown in FIG. 3.
Then, the pouring sleeve 109 is horizontally swung or moved until the
opening thereof is separated substantially apart from the molds. At such a
position, the pouring sleeve 109 can be cleaned by spraying, or lubricant
can be applied thereto.
The inlet 106 communicates with the outside of the molds through a passage
113 which is formed horizontally in the stationary mold 103 so as to have
one of its openings at the runner portion 107. Thus, molten metal is
supplied from an external source through the passage 113 to the inlet 106.
The inner periphery of the horizontally-formed passage 113 is slightly
tapered so that the passage 113 becomes wider toward the movable mold 105
and that all the molten metal in the passage flows down to the inlet 106.
A valve means 114 is provided in the passage 113, near the inlet 106. The
valve means 114 includes a valve seat 115 and a valve 116. The valve seat
115 is formed so as to become wider toward the movable mold 105. The valve
116 is formed so as to be seated on the valve seat 115 and is movably
supported in the movable mold 105. The valve 116 is connected, by a
screwing means, to a piston rod 118 of a cylinder (a device for driving
the valve means) 117 which is connected at one of its ends to the movable
mold 105. The valve 116 is slid through a guide bush 119. Instead of the
cylinder 117, a solenoid may be used.
The passage 113 also functions as a well. The horizontal passage 113 is
connected, at its upstream end and its bottom-side periphery, to a duct
120 which slopes down toward a supplying unit 123. The duct 120 comprises
an inner liner 121. The inner liner 121 comes into direct contact with the
molten metal and is formed of ceramic or heat resisting metal (e.g.,
SKD61). An induction heating coil (an induction heater) 121a and a heat
insulating member 121b are provided around the inner liner 121. Such an
induction heating coil or an inner liner made of ceramic or heat resisting
metal may be provided around the passage 113 in the stationary mold 103.
The duct 120 sloped so as to convey molten metal to the passage 113 is
connected to a horizontal duct 122, which is connected to the supplying
unit 123. The supplying unit 123 comprises a tank 124 for storing molten
metal and a pump means 125 for pumping out the molten metal stored in the
tank 124. The pump means 125 includes a cylinder barrel 127, a piston 126
inserted in the cylinder barrel 127, and a cylinder 128 for moving the
piston 126 up and down. The storing tank 124 is connected through a
suction inlet 130 and a passage 129 to the inside of the cylinder barrel
127. The suction inlet 130 is opened or blocked by a rod valve 131. The
rod valve 131 is moved up and down by a valve cylinder 132. The molten
metal in the cylinder barrel 127 is conveyed through a passage 133 and a
check valve 134 to the horizontal duct 122. The horizontal duct 122 is
equipped with a heater 135.
Inside the stationary mold 103, a movable rod 136 is provided at one of the
ends of the passage 113, the end closer to the stationary board 102. A
cylinder 137 is fixed to the stationary board 102. The rod 136 is
protruded into or retracted from the passage 113 by the action of the
cylinder 137. A gas passage 138 is formed inside the rod 136, as shown in
FIG. 3. One of the ends of the passage 138, i.e. the end closer to the
cylinder 137, is connected by a connecting means 139 to a source 99 of
inert gas such as nitrogen (not shown). The openings at the other end (the
downstream end) of the gas passage 138 are provided at the outer periphery
of the front end portion of the rod 136. Thus, when the rod 136 is
protruded into the passage 113 which becomes wider toward the movable mold
105, the nitrogen is supplied from the openings of the gas passage 138 to
the mold cavity 108 through a gap between the outer periphery of the front
end portion of the rod 136 and the tapered inner periphery of the passage
113. A ventilation passage 146 is formed in the stationary mold 103 so as
to communicate with the outside. The inside opening of the passage 146 is
provided at a portion of the passage 113 where the rod 136 is slid
through. When the rod 136 is retracted, the ventilation passage 146 is
opened to connect the passage 113 to the atmosphere.
A pin 140 for feeding is connected to a cylinder 141 provided in a portion
of the stationary mold 103. The cylinder 141 protrudes and retracts the
pin 140. Numeral 142 denotes a product pushing-out means including a
pushing pin 143. A known gas remover 144 is connected to the mold cavity
108 through a gas removing passage 145 formed on the mating surfaces of
the molds 103 and 105.
The operation of the diecasting apparatus constructed as described above
will be described. If the rod valve 131 is held up and the piston 126 is
raised, the molten metal M stored in the tank 124 flows into the cylinder
barrel 127. The check valve 134 provided at the junction of the passage
133 and the duct 122 keeps the molten metal M in the ducts 120 and 122
from flowing back to the cylinder barrel 127.
Then, the valve 116, the feeding pin 140 and the pushing pin 143 are drawn
back to predetermined positions beforehand, and the molds 103, 105 are
clamped as shown in FIG. 3. In a condition where the pouring sleeve 109 is
connected to the bottom of the molds 103 and 105, the cylinder 137 is
operated to project the rod 136 until the outlets of the gas passage 138,
i.e. the tip portion of the rod 136, reach the tapered inner periphery of
the molten-metal passage 113. Then, the inert gas such as nitrogen gas is
let out of the outlets of the gas passage 138, e.g. by operating not-shown
valves, into the mold cavity 108, the pouring sleeve 109, etc., until the
inert gas (nitrogen) has completely replaced the air therein.
Next, the suction inlet 130 is closed by the rod valve 131, and the valve
means 114 is opened by drawing back the valve 116. While such a state is
maintained, if the piston 126 is lowered, the molten metal M flows out of
the cylinder barrel 127 through the passage 133, the check valve 134, the
ducts 122 and 120, the passage 113, the runner portion 107 and the inlet
106 to the pouring sleeve 109. Preferably, the injection plunger 111
should be raised to its uppermost position beforehand and lowered
gradually as the molten metal M flows into the pouring sleeve 109. Such
operation substantially prevents the molten metal from violently flowing,
splashing, taking in air, losing its heat, etc. As the molten metal flows
into the pouring sleeve 109, the nitrogen therein is forced out to the
mold cavity 108 and then let out through the gas remover 144.
If the descend piston 126 comes to a stop, all the molten metal in the
passage 113 flows down to the pouring sleeve 109 since the inner periphery
of the passage 113 is tapered, and the molten metal remaining in the duct
120 fills the duct 120 up to the top thereof. Thus, the next supplying
operation can be started quickly, and with less preparation.
When a sufficient amount of the molten metal is stored in the pouring
sleeve 109, the operation of the pump means 125 is stopped. As mentioned
above, all the molten metal in the passage 113 having a tapered inner
periphery flows into the pouring sleeve 109, and the molten metal
remaining in the duct 120 fills the duct 120 to the top thereof.
Then, the valve means is closed by placing the valve 116 onto the valve 115
as shown in FIG. 6. The rod 136 is retracted to the position as shown in
FIG. 6. While such a state is maintained, the injection plunger 111 is
raised to inject the molten metal M into the mold cavity 108. As the
molten metal is injected into the mold cavity 108, the nitrogen therein is
forced out to the atmosphere through the gas removing passage 145 and the
gas remover 144. When the surface of the molten metal M reaches a position
adjacent to the gas remover 144, the valve of the gas remover 144 is
closed by the inertia force of the molten metal or an electrical signal.
Thus, the molten metal does not get into the gas remover 144 nor does it
go outside. Cavitation does not occur in the molten metal nor in the cast
product.
According to this embodiment, the valve means 114 prevents the molten metal
M from flowing back to the passage 113 or the storing tank 124, despite
the pressure caused by the injection. Also, should the molten metal flush
into the passage 113 though a leak or gap in the valve means 114 during
the high pressure injection or casting, the impact which the air in the
passage 113 receives from the molten metal flushing in will be released
through the ventilation passage 146, since the rod 136 is retracted so
that the ventilation passage 146 communicates with the passage 113. Thus,
the molten metal in the duct 120 will not be affected even in such a case.
The above-mentioned incidental leak or gap may be caused, e.g. by a tiny
fin deposited on a valve means 114.
During the injection, a feeding operation is performed by operating the
cylinder 141 to project the feeding pin 140 while the mold cavity 108 is
filled with the molten metal M.
The molten metal in the mold cavity 108 is left to solidify and cool for a
predetermined time after the injection. Then, while the molds are opened
as shown in FIG. 7, the passage 113 is cleaned by the following procedure:
operating the cylinder 137, as the molds are moved apart, to project the
rod 136 until the rod 136 completely covers the opening of the duct 120 at
the passage 113; and then spraying nitrogen gas, air or a lubricant
through the gas passage 138 into the passage 113. After the cleaning
operation, the cast product is taken out. For the next diecasting
operation, the molds are clamped, and the molten metal is supplied into
the pouring sleeve 109, as described above. Since the molten metal left in
the ducts 120, 122 has been maintained at a required temperature by the
induction heating coil 121a and the heater 135, the molten metal can be
pumped to the inlet 106 immediately when desired.
Also, immediately after the pouring sleeve 109 is filled with the molten
metal M, the injection operation can be started simply by closing the
valve means 114. Thus, the diecasting operation can be quickened, and a
temperature decrease in the molten metal stored in the pouring sleeve 109
can be avoided, so that partial solidification of the molten metal is also
avoided. As a result, the quality of the products is upgraded.
As can be understood from the illustration in FIG. 3, the molten metal
stored in the tank 124 is conveyed to the pouring sleeve 109 without being
exposed to the atmosphere. Therefore, even molten metal easy to oxidize,
such as aluminium or magnesium, can be cast without any oxidization,
according to this embodiment. Also, a wide variety of metals can be cast,
and the defects caused by oxide are eliminated. As a result, high-quality
cast products are obtained.
According to this embodiment, the valve 116 may be provided with a cooling
means, e.g. of a water-cooling type, in order to protect the valve 116
from the heat of the molten metal.
As shown in FIGS. 3 through 7, the inner peripheral surface of the passage
113 is tapered so as to become wider downstream, according to this
embodiment. There is nothing to block or obstruct the smooth flow of the
molten metal through the passage 113 (or the passage 30). Thus, no molten
metal will be left in the passage 113 when the supplying operation is
stopped.
Since the movable mold 105 is moved horizontally away from the stationary
mold 103 (the horizontal type), according to this embodiment, when the
cast product is to be taken out, the solidified metal (biscuit) located
lower than the valve means 114 (toward the inlet 106) can be taken out
together with the cast product.
As shown in FIG. 3, the pouring sleeve 109 according to this embodiment is
connected to the inlet 106 so that it is always positioned vertically and
never tilts during the diecasting operation. Thus, a substantial amount of
molten metal can be stored in the pouring sleeve 109. The pouring sleeve
109 does not need to be as long as that of a known art. The pouring sleeve
109 can assume a position in which the inside thereof can be cleaned, by
lowering it from the molds 103, 105 and pivoting it about the rotational
center at a lower portion of the injection unit 110.
Although the molds are of the horizontal type in the above embodiments, the
molds may be of the vertical type in which the movable mold is moved up
and down.
As described above, since molten metal is conveyed through a closed
passage, i.e. the duct, the passage and the inlet, into the pouring sleeve
in the diecasting apparatus according to the present invention, the molten
metal never leaks or spills. Also, since the molten metal is never exposed
to the atmosphere during a pouring operation, even a metal easy to
oxidize, such as magnesium, can be cast without oxidization. Naturally,
the defects caused by oxide can be eliminated.
Since the time required for the pouring operation is substantially short
according to the present invention, the casting cycle can be quickened,
and also, with the temperature of the molten metal to be poured can be
maintained sufficiently high. As a result, high-quality cast products can
be obtained.
According to the present invention, favorable sealing of the passage
provided in the stationary mold prevents leakage of molten metal from the
passage.
According to the present invention, since the pouring sleeve is always
positioned vertically, the pouring sleeve can store a substantial amount
of molten metal or may be made relatively short while still retaining a
required capacity.
A check valve may be provided in a portion connecting the duct to the
supplying unit in order to enhance the prevention of flowing-back. Since
the molten metal left in the ducts is maintained at a required temperature
by the heater provided thereon, such molten metal can be immediately used
for the next diecasting operation.
While the present invention has been described with respect to what is
presently considered to be the preferred embodiments, it is to be
understood that the invention is not limited to the disclosed embodiments.
To the contrary, the invention is intended to cover various modifications
and equivalent arrangements included within the spirit and scope of the
appended claims. The scope of the following claims is to be accorded the
broadest interpretation so as to encompass all such modifications and
equivalent structures and functions.
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